In
1859, a severe solar storm called the Carrington
Event occurred throughout September 1 and 2. It is the most
powerful solar storm recorded in history. Offices caught on fire and
telegraph operators were actually shocked and saw sparks from the
storm. Sunspots and solar flares were seen on the sun from August 28
through September 2, and aurorae seen over the Rocky Mountains were
so bright that gold miners awoke early because they thought it was
daylight. Just before noon on September 1, Richard Carrington, a
British astronomer, saw the largest flare in the sky. This large
flare caused a coronal mass ejection, which is a billion-ton solar
storm cloud, which took 18 hours to travel toward Earth.

A
report composed in 2008 by the National
Academy of Sciences noted that a solar storm as severe as
the Carrington Event could cause mass power blackouts and "permanent
damage" to main transformers if it were to occur today. In fact,
in 1989, Quebec experienced a geomagnetic storm much less powerful
than the Carrington Event, and even still, power was knocked out for
over nine hours and transformers were damaged in Quebec, Great
Britain and New Jersey. In 2003, yet another geomagnetic storm milder
than the Carrington Event occurred, causing transformer damage in
South Africa and blackouts in southern Sweden.

Unfortunately,
a report composed by the North
American Electric Reliability Corporation (NERC) and
the U.S. Department of
Energy in 2009 warns that modern power systems, though
several utilities have taken the necessary steps to strengthen and
secure their power grids, have a "significantly enhanced
vulnerability and exposure to effects of a severe geomagnetic storm."

To
protect power systems in the event that another powerful solar storm
should occur, NASA has developed a project called "Solar
Shield," which has the potential to shelter high-voltage power
lines that crisscross over North America. Considering the length of
these power lines has "increased nearly 10 fold" since the
beginning of the Space Age, it is critical to consider the affect a
solar storm could have on power systems in the United States and
throughout the world.

"Solar
Shield is a new and experimental forecasting system for the North
American power grid," said Antti Pulkkinen, project leader
and Catholic University of
America research associate currently working with NASA's
Goddard Space Flight Center. "We believe we can zero in on
specific transformers and predict which of them are going to be hit
the hardest by a space
weather event."

Geomagnetically
induced currents (GICs) are the main problems when it comes to power
grids during geomagnetic storms. When a CME approaches Earth's
magnetic field, it causes the field to shake. This quiver causes
currents from the ground to Earth's upper atmosphere, and powerful
GICs can trip breakers, overload circuits and melt the windings of
transformers. Transformer damage leads to large-scale blackouts, and
these transformers cannot be repaired in the field. They must be
replaced, which is both expensive and time consuming.

"Solar
Shield springs into action when we see a coronal mass ejection (CME)
billowing away from the sun," said Pulkkinen. "Images from
SOHO and NASA's twin STEREO spacecraft show us the cloud from as many
as three points of view, allowing us to make a 3D model of the CME,
and predict when it will arrive."

The
CME typically takes 24 to 48 hours to cross the Sun-Earth divide.
During this time, NASA researchers at the Goddard
Community Coordinated Modeling Center (CCMC) are gathering
physics-based computer programs to model the CME. Thirty minutes
before impact, ACE, a spacecraft stationed 1.5 million km "upstream
from Earth," uses its sensors to make in
situ measurement's
of the CME's magnetic
field, density and speed, then sends the data to the Solar Shield
team on Earth. The data is fed into CCMC computers where models
predict currents and fields in Earth's upper atmosphere and transmit
this information to the ground. The Solar Shield team is then
prepared to send alerts to utilities with details about the
GICs.

"We'd
like more power companies to join our research effort," said
Pulkkinen. "The more data we can collect from the field, the
faster we can test and improve Solar Shield."

Solar
Shield has never been tested during a geomagnetic storm, but a small
number of utilities have already installed monitors at main locations
in the power grid so that the team can check their predictions.
Pulkkinen and his team expect the
next solar maximum around 2013.